Did you know the United States Marshals Service and the Federal Bureau of Prisons assign register numbers to federal prisoners? These numbers are important for loved ones to know if they want to visit an inmate or send money or mail to an inmate.

These eight-digit codes follow this format: XXXXX-OXX.

While the first five numbers in the register number are unique, the last 3 indicate the district where the offender was arrested and or processed into the federal correctional system.

Below are the different codes for the various district locations.

If you aren’t sure what an inmate’s register number is, you can always find it on the Federal Bureau of Prisons’ website on the Find an Inmate page. Click the “Find by Name” tab to perform a search by name. You will also require the race, sex and age of the inmate.